If you are legally married on or before 12/31/2018 then you can only file as Married Filing Jointly or Married Filing Separately.
If she does not have a SS number or an ITIN and you are not applying for an ITIN using IRS Form W-7 with your tax return then you can only file as Married Filing Separately.
If you do apply for an ITIN with a Form W-7 with your tax return then you can file as Married Filing Jointly. She would have to enter her income from all sources, US or Foreign, in US dollars on the tax return. If she worked and lived outside the US and has a foreign employer then she reports her Foreign Earned Income on IRS Form 2555 which is included as part of your personal tax return, Form 1040. Up to $104,100 Foreign Earned Income is excluded from being taxed in 2018.
